In the recent years, the Multiple-Input Multiple-Output (MIMO) techniques have emerged as an important research field for enhancing the throughput of in-home Power Line Communication (PLC) systems by exploiting the additional Protective Earth wire. The development of such systems requires an accurate description of the noise in the propagation channel. This paper presents two statistical models for the background noise found in MIMO PLC channels, based on noise measurements performed in five houses. In the proposed models, the spectral characteristics of MIMO background noise are presented, in 2-150 MHz range, following two existing formalisms for Single-Input Single-Output SISO) PLC noise.